1. Field of the Invention
This invention relates to a manual optical rotary encoder. More particularly, it relates to an optical rotary encoder including a control pulse generator portion and a selector switch portion which are of the unitary construction.
2. Description of the Prior Art
A video tape recorder has a variety of modes of tape operation, including rewind, fast forward, playback and pause. If a mode selector switch is actuated to select a particular mode, the corresponding control signal is fed to a motor so that a tape may travel at a particular speed in a particular direction, or pause. It is often desirable to watch a particular portion of a recorded tape at a desired tape speed for editing or other purposes. The selection of a particular mode by the mode selector switch is insufficient for the minute control of tape travel and a lot of time is required for locating the beginning of any such desired tape portion. In order to avoid any such inconvenience, it is necessary to provide additionally a manual control pulse generator for adjusting the control signal to be fed to the motor. In other words, two different signal generators are provided, i.e., mode selector switch and control pulse generator. The mode selector switch enables the tape to travel at a selected speed. The control pulse generator generates a control pulse if its operating shaft is rotated at a desired speed. This pulse is added to, or deducted from, the control signal to be fed to the motor and thereby enables the tape to travel at a speed which differs from that selected by the mode selector switch.
The mode selector switch and control pulse generator which are known in the art are shown by way of example in FIGS. 2 and 3, respectively. Referring first to FIG. 2, the mode selector switch has a shaft 16 to which a leaf spring 17 and a spring seat 18 are secured. A plurality of steel balls 19 are disposed between the spring seat 18 and a front plate 20. The steel balls 19 are urged by the spring 17 toward the front plate 20, whereby a click mechanism is formed. An upper base plate 21 is secured to one end of the shaft 16 and carries a movable contact 22. A lower base plate 23 faces the upper base plate 21 and the contact 22 is disposed therebetween. The lower base plate 23 is connected to the front plate 20 by bolts 24. The shaft 16 is rotatably supported on the front plate 20 and the lower base plate 23 by an upper bearing 25 and a lower bearing 26, respectively. A plurality of fixed contacts not shown are provided on the lower base plate 23. If the shaft 16 is rotated to cause the click mechanism to achieve a click motion, the movable contact 22 is rotated with the upper base plate 21 to slide on the fixed contacts on the lower base plate 23. The combination of the movable contact 22 with each fixed contact enables the selection of a particular mode of tape operation.
Referring now to FIG. 3, the control pulse generator has a shaft 27 which is rotatably supported by bearings 28 and a code plate 29 having a circumferential slit is provided on the shaft 27. The code plate 29 is rotatable with the shaft 27. The bearings 28 are held in a housing 30 attached to a printed base 31. Another printed base 32 faces the printed base 31 and is connected thereto by a cover 33. A plurality of light emitting elements 34 are provided on the lower printed base 32, and a plurality of light receiving elements 35 on the upper printed base 31. The light emitted by the light emitting elements 34 reaches the light receiving elements 35 through the slit of the code plate 29. As a result of the transmission of light through a particular slit, or its interruption between two slits, the corresponding light receiving element 35 produces a particular output pulse.
The mode selector switch and the control pulse generator are assembled separately from each other and mounted on a common panel in close proximity to each other. Insofar as they are separate devices, however, they require a large space for installation and a complicated process for assembly. Moreover, they present inconvenience in operation. In order to join them into a single unit, it is not sufficient to connect the shafts 16 and 27 thereof, since the unit is not only unreasonably large, but very difficult to assemble.
It is not only for the editing of a tape in a video tape recorder that the two signal generators are required. Two such signal generators are also required when, for example, an automobile radio is tuned so that the frequency may be manually adjusted and automatically selected by the selector switch.